Method of improving the uniformity of an unopened tow band and apparatus for making cigarette filters therefrom



y 1968 G. A. WATSON, JR 3,384,932

METHOD OF IMPROVING THE UNIFORMITY OF AN UNOPENED TOW BAND AND APPARATUS FOR MAKING CIGARETTE FILTERS THEREFROM Filed Feb. 28, 1964 United States Patent 3,384,932 METHOD OF IMPROVING THE UNIFORMITY OF AN UNOPENED TOW BAND AND AEPARA- TUS FOR MAKING CIGARETTE FILTERS THEREFROM George A. Watson, Jr., Charlotte, N.C., assignor to Celanese Corporation of America, New York, N.Y., a corporation of Delaware Filed Feb. 28, 1964, Ser. No. 348,219 9 Claims. (Cl. 19-65) This invention relates to a new method and apparatus for processing tow into cigarette filter rods. More particularly, this invention relates to the manufacture of cigarette filter rods which are improved in uniformity per unit rod length of weight and pressure drop across the length of the rod and, consequently, to the manufacture of cigarette filter tips improved in uniformity from tip to tip in weight, pressure drop across the length of the tip and smoke removal efiiciency; this invention also relates to apparatus suitable for the effecting of the method of manufacture of the cigarette filter rods and tips of improved uniformity.

The term unopened tow band describes a large number of aligned, continuous, crimped filaments which are associated in a fiat band-like structure. The term subband describes a smaller band which is split off from the larger band, i.e., the unopened tow band.

Tows suitable for cigarette filters range from about 35,000 to 160,000'total denier. The filament sizes normally available are usually in the range of about 2 to 75 denier per filament and the tow may be made up of between about 5,000 and 100,000 filaments of from about 2 to 16 denier per filament or a total denier within the range of about 35,000 to 160,000. The crimps in the tow can range up to about 30 to 40 but preferably is from about 4 to 25 crimps per inch.

Normally, the unopened tow band is provided in the form of a bale in which the unopened tow band is continuously folded upon itself.

Any of the operations by which the crimp is conventionally put into the unopened tow band causes the filaments adjacent to each other to have the identical crimp configuration. This results frequently in forming bundles of filaments here and there in the tow that cling together and are difficult to separate in subsequent operations. This condition wherein adjacent filaments have identical crimp is known as crimp registration. Opening is the term used to described the deregistering of the crimp.

Several r011 systems, which Will subsequently be de scribed, are available which deregister crimp with varying degrees of success. By the methods and apparatuses of the present invention, it has now been found possible to further randomize the crimp whereby the uniformity of cigarette filter rods and the filter tips manufactured therefrom is improved.

Thus, it is an object of this invention to provide new methods and apparatuses for processing unopened tow band into cigarette filter rods of improved uniformity per unit rod length of weight and pressure drop across the length of the rod and consequently into tips of improved uniformity from tip to tip in weight, pressure drop across the length of the tip and smoke removal efficiency.

Further objects will appear from the present description and claims.

In accordance with the objects of this invention, it has now been found that by providing a plurality of sources of sub-bands (i.e., unopened tow bands of fewer than the number of filaments normally used in the manufacture of cigarette filter rods and tips, the total number of filaments in all of said sub-bands being said number of filaments normally used in said manufacture), said sources being, for example, bales, leading a plurality of sub-bands each from a separate bale, combining said sub-bands into a single band, feeding said single band to a tow opener, opening said single band by means of said tow opener and compacting the thereby opened band to form cigarette filter rod (from which tips may subsequently be made by cutting said rod into suitable lengths) and means suitable for carrying out this method, cigarette filter rods and tips of improved uniformity of weight, pressure drop and smoke removal efficiency are manufactured.

It has also been found that similar desirable improvement in uniformity is achieved by providing a single, conventional unopened tow band, splitting said unopened tow band into a plurality of sub-bands, leading said sub-bands through a plurality of paths, recombining said sub-bands into a single band, feeding said single band to a tow opener, opening said single band by means of said tow opener and compacting the thereby opened band to form cigarette filter rod, the number of said paths being no greater than the number of said sub-bands and at least one of said paths being different in length from the remainder of said paths, said path lengths thereby comprising a base length and at least one extended length. By base length is meant the shortest of said path lengths and by extended length is meant any longer path length.

In the drawings:

FIG. 1 is a schematic plan view of the apparatus used in the embodiment of the invention wherein the unopened tow is supplied in the form of sub-bands, one from each of a plurality of sources.

FIG. 2 is an illustration of the method and apparatus used in the embodiment of the invention wherein the unopened tow is supplied as a single band which is subsequently split into a plurality of sub-bands.

To describe FIG. 1 in greater detail, unopened tow sub-bands 12 and 13 are fed from bales 10 and 11, respectively, in piggyback relationship, sub-band 12 over sub-band 13, into conventional overhead banding jet 15 wherein the sub-bands are combined into a-single band 14. Band 14- is fed through the conventional threaded roll system comprising roll sets 16 and 17 which are the same as the threaded roll sets referred to with regard to FIG. 2. Resultant open tow band 18 is subjected to the conventional compacting and cutting 30 operations whereby cigarette filter rods and tips are made.

To describe FIG. 2 in greater detail, unopened tow band 20 is supplied from a bale (not illustrated), widened and flattened in a conventional overhead banding jet (not illustrated) and passed over tension bar 25 and then between the nip of hydraulic drag rolls 27 which also function as tow feed means. Thereafter, the tow band is split (this may :be done at start-up by hand) into four sub-hands 21, 22, 23 and 24, two alternating bands of which are directed straight to threaded roll system 28 (which comprises two contiguous pairs of rolls, the bottom roll of which is rubber-surfaced steel and the top roll of which is steel the surface of which is in the configuration of a continuous helical ridge (not illustrated)) and the other two of which are diverted over tension bar 26 before being passed through threaded roll system 28. The threaded roll system opens each tow sub-band. When the sub-band is hand split, which is often the more desirable procedure, the splitting means is effected by the coaction of drag rolls or feed means 27, tension bar 26 and threaded roll system 28. Therefore, tension bar 26 effects the continuation of splitting because once the splitting is initiated, the splitting continues as long as different paths are taken by the different sub-bands. The generally parallel lengthwise alignment of the continuous filaments in tow band 20 lends itself to such continuous operation. As illustrated, the first pair of rolls of the threaded roll system recombines the tow sub'bands into a single band. After the tow is passed through the threaded roll system, it is lead to sub-sequent operations such as compacting and cutting 30 whereby cigarette filter rods and tip-s are manufactured.

The threaded roll system for opening tow is fully described in United States Patent No. 3,032,829 to Mahoney et 211., issued May 8, 1962, and the disclosure of that patent is herein incorporated by reference. Thus, for example, the ridge in the threaded rolls may be helical or in the form ofv parallel endless circles or ellipses.

The embodiment of the present invention illustrated in FIG. 2 is actually a combination braked roll-threaded roll system, though a threaded roll system may be used alone. Thus, the pair of hydraulic drag rolls constitute the braked rolls. Thus, there are two opening zones, that between and including the threaded rolls and that between the hydraulic drag rolls and first threaded rolls. In the first of these opening zones, the Opening of the tow is effected by the tension exerted on the tow between drag rolls 27 and the first pair of the faster rotating rolls of threaded roll system 28; the tension causes the crimp or part or most of the crimp to be temporarily removed and when the tension is subsequently decreased or removed, part, most or all of the original crimp is restored but now the filaments do not lie together so regularly and the crimp has been deregistered. A braked roll system comprising one or more sets of hydraulic drag rolls and one or more sets of unthreaded conventional draw rolls may be used alone to open the tow instead of either a threaded roll system or a combination braked roll-threaded roll system.

Instead of splitting the tow by hand at startup, the tow could be split by other means; e.g., there could be provided a banding jet with at least one slit substantially parallel to the length of the tow associated with means for feeding compressible fluid (preferably a gas or a vapor) to said slit whereby the stream or streams of air thus formed split the tow band into a plurality of subbands, one split being formed by each stream. Subsequent to such an operation, it may be found that there are residual crossovers (i.e., stray filaments extending between tow sub-bands); these crossovers" may be cut by providing relative opposite motion between the longitudinally moving tow sub-hands, on the one hand, and suitable cutting means inserted between the tow subbands, on the other hand, e.g., by providing stationary heated blades between the longitudinally advancing subbands.

In the embodiment illustrated in FIG. 2, the length of a tow sub-band between its exit from the nip of rolls 27 and its entrance to the nip of the first set of rolls of threaded roll system 28 is the base length, i.e., the shortest path which any sub-band traverses when not joined in a single band, and the length of a tow sub-band between said two points but as diverted over tension bar 26 is the extended length," i.e., any path which a subband traverses which is longer than the base length.

In order to obtain the best results, it is preferred that each extended length be at least about 1% longer than at least one other path length. It is also preferred that each extended length be no more than about 250% longer than the next shorter path length. At differences substantially less than 1%, significant improvement in uniformity is not achieved. At differences substantially greater than 250%, it becomes necessary either to use an impractically large amount of floor space or to divert sub-bands so sharply that they are likely to break from the resultant increase in tension.

There may be but one extended length (i.e., but one diverted sub-band and thus a total of two sub-bands) or there may be one undiverted subband and a plurality of diverted sub-bands or a plurality of undiverted sub-bands and one diverted sub-band. There may be one extended path or path length or a plurality of extended paths or path lengths.

The preferred material of which the tow used in the method of the present invention is comprised is continuous filaments of cellulose acetate (i.e., the well-known secondary cellulose acetate of commerce having an acetyl value, calculated by weight as combined acetic acid, of to 59.5%). However, filamentary material of other esters or others of cellulose may be used, such as cellulose triacetate, cellulose propionate, cellulose acetate propionate. Furthermore, other filamentary materials may be used, such as rayon (regenerated cellulose), linear superpolyamides such as nylon-6 and nylon-66, linear polyesters, acrylonitrile polymers and copolymers, polyolefins and the like.

When the sub-bands are recombined into a single band at the tow opening Zone, they may be recombined into their former side-by-side relationship, as illustrated in FIG. 2, or they may be combined on top of one another, which embodiment may be termed piggyback, and in either embodiment be successfully opened.

The invention is further illustrated in the following examples:

Example I Tow sub-bands from two bales of 26,400 total denier, 3 denier per filament cellulose acetate continuous hollow filament tow are combined into a single band in the manner illustrated in FIG. 1 in order to make a single tow band of 52,800 total denier. (The hollow cross-section of the filaments was obtained by dry spinning the cellulose acetate dope through C-shaped orifices; the resultant C- cross-sectioned streams fold closed at their tips as the spinning solvent evaporates and thus the resultant filaments are of hollow cross-section.) Said single tow band is passed through a conventional threaded roll system wherein it is opened. The resultant opened tow band is compacted and cut by conventional machinery into cigarette filter rods and tips. Randomlyselected experimental tips show only a 6 mm.(H O) range of pressure drop, which is approximately half of the normally encountered range.

Example II A bale of 5.0 denier per filament, 48,000 total denier cellulose acetate continuous filament tow is processed in the apparatus illustrated in FIG. 2. The tow is first passed through. a conventional overhead banding jet (not illustrated) for flattening and widening the tow from the bale (not illustrated), then against the top tension bar, then through the nip of the drag rolls. At this point the tow is split, in a series of runs into two, three or four subbands. In said series of runs, adjacent sub-bands are alter nately passed directly into the nip of the first pair of rolls of the threaded roll system or against the bottom tension bar and then into the nip of said first pair of rolls. The bottom tension bar is approximately 11 inches above the regular tow path. This causes the diverted to'w sub-bands to traverse a path length 12" longer than the regular tow path length between the drag rolls and the first pair of rolls of the threaded roll system (center-to-center distance), said regular tow path length being approximately 12". The runs may be summarized as follows:

(A) No splits (control).

(B) 1 split, sub-bands recombined side-by-side. (C) 1 split, sub-bands recombined piggyback. (D) 2 splits, sub-bands recombined side-by-side. (E) 2 splits, sub-bands recombined piggyback. (F) 3 splits, sub-bands ercombined side-by-side. (G) 3 splits, sub-bands recombined piggyback.

Several thousand filter rods, using conventional filter rodmaking machinery, are made from the tow in each run. No processing difficulties are encountered. Laboratory analysis of the rods indicate that an average reduction in rod pressure dropvariability of 57% is accomplished using the splitting techniques. A 5l% average improvement in rod Weight control is also noted. Smoke removal efficiency tests indicate that the experimental rods are at least as effective as the control rods and, furthermore, with an average weight savings of about 2%.

It is to be understood that the foregoing description of the present invention is given for the purpose of illustration only and that many changes may be made in the invention without departing from the spirit thereof.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of improving the uniformity of an unopened tow band comprising splitting an unopened tow band into a plurality of sub-bands, leading at least one of said sub-bands through a different path than another subband, one of said paths being at least one percent longer in length than one other path, recombining and feeding said substantially unopened sub-bands to a tow opener to form a single band and opening said single band by means of said tow opener, thereby forming a uniform opened tow.

2. The method of claim 1 wherein the opened tow band is compacted and formed into a cigarette filter rod.

3. The method of claim 1 wherein the path of at least one sub-band is a maximum of about 250 percent longer than the next shorter path length.

4. The method of claim 1 wherein the unopened tow band is first passed over a tension pin and then through the nip of a pair of drag rolls before being split.

5. The method of claim 1 wherein the unopened tow band is formed from a plurality of tow bands.

6. An apparatus for making a cigarette filter rod of improved uniformity comprising unopened tow band feed means, tow splitting means for dividing the tow into subbands, tow opening means and means for compacting opened tow to form a cigarette filter rod, wherein an unopened tow band from said feed means is split into a plurality of sub-bands which are directed in diverse paths of unequal length and subsequently recombined wherein the tow band feed means and tow opening means forms a path for at least one sub-band and wherein the tow feed means, tow splitting means, and tow opening means forms a sec- 0nd path of greater distance for at least one other subband.

7. The apparatus of claim 6 wherein the tow splitting means comprises at least one tension pin out of alignment with the direct path between the tow feed means and tow opening means.

8. The apparatus of claim 6, wherein the tow opening means comprises a ridged row tow opening system.

9. The apparatus of claim 6 wherein the tow opening means comprises a helically ridged row tow opening system.

References Qited UNITED STATES PATENTS 2,219,804 10/1940 Boyce 28-40 X 2,801,638 8/1957 Schur et al. 131-208 2,999,503 9/ 1961 Schur et al 131-208 3,032,829 5/1962 Mahoney et al. 19-65 3,144,025 8/ 1964 Erlich.

3,156,016 11/1964 Dunlap et al 19-66 2,811,770 11/1957 Young 28-72 X 2,822,582 2/1958 Hayward et al. 19-65 3,255,506 6/1966 Fritz 19-66 DORSEY NEWTON, Primary Examiner. 

5. THE METHOD OF CLAIM 1 WHEREIN THE UNOPENED TOW BAND IS FORMED FROM PLURALITY OF TOW BNDS. 